Table 5. — Pink; shrimp in monthly trawl catches from eight stations in Whitewater Bay, September 



1968 to April 1969 



Month 



Stations 



Total 



1,888 

 1,585 

 1,461 

 1,918 

 1,379 

 1,013 

 1,011 

 490 



Total 



267 



416 



4,176 



4,708 



9,738 



10,745 4,578 



1,081 35,709 



Analysis of variance of the transformed data 

 for the eight stations indicates highly significant 

 differences in the geometric mean catches 

 among months and among stations. Differences 

 among months reflect a general seasonal de- 

 cline in abundance over the 8-month period. 

 Differences in the geometric mean catches 

 among stations are apparently related posi- 

 tively to the kinds and density of the vegetative 

 cover. Stations 5 and 6 with extensive vegetative 

 cover had significantly larger catches of 

 shrimp than those stations with less 

 cover. 



Growth. -- We studied growth of pink shrimp 

 in the estuary by holding a population of shrimp 

 in a 0.1-hectare (l/4-acre) enclosure in Coot 

 Bay and sampling it at weekly intervals. The 

 site for the enclosure (marked E in fig. 13) 

 was selected in an area normally inhabited by 

 shrimp and where conditions within the en- 

 closure could be maintained as closely as 

 possible to the natural environment. 



We completed the enclosure in late October 

 and stocked it with 20,000 postlarval pink 

 shrimp caught in Buttonwood Canal on Octo- 

 ber 30. Samples of about 200 shrimp were 

 taken each week with plankton nets. From 

 October 30 through April 17 (24 weeks) the 

 average carapace length (the distance from the 

 orbital notch to the posterior edge of the 

 cephalothorax) of the shrimp increased from 

 1.8 to 15.6 mm. (0.1 - 0.6 inch) (fig. 14). Shrimp 

 collected on April 17 were 6.5 to 21.4 mm. 

 (0.3 - 0.8 inch) carapace length. 



After the seventh week and until the end of 

 the experiment, temperatures in the enclosure 

 were recorded continuously with a Ryan therm- 

 ograph. Weekly averages ranged from 19.9° C. 

 (68° F.) in mid-March to 24.4° C. (76° F.) in 

 late March; the average value for the experi- 

 ment was 21.7° C. (71° F.). Salinity in the 

 enclosure ranged from 4.9 p.p.t. in early 

 November to 21.7 p.p.t. in late March. The 



average salinity for the experimental period 

 was 14.5 p.p.t. 



The summer growth experiment (now 

 underway) was started on May 27 when an esti- 

 mated 19,500 postlarvae were captured in 

 Buttonwood Canal and placed in the enclosure. 

 Inspection of the early samples suggests that 

 shrimp growth was considerably faster in the 

 summer. 



C. P. Idyll and B. J. Yokel 

 Project Leaders 



Institute of Marine Sciences, 



University of Miami 

 (Contract No. 14-17-0002-279) 



ESTUARINE PROGRAM 



Analysis of past data was completed during 

 the fiscal year. Manuscripts entitled "Hydro- 

 graphic survey of the Galveston Bay system, 

 Texas, 1963-66" and "Relative abundance, 

 seasonal distribution, and species composition 

 of demersal fishes of Louisiana and Texas, 

 1962-64" are almost ready for submission to 

 the Technical Editors. 



Publications released since July 1, 1968, 

 were: "Hydrographic observations from the 

 Galveston Bay system, Texas, 1958-67," "Use 

 of dorsal carinal spines to differentiate between 

 postlarvae of brown shrimp, Penaeus aztecus 

 Ives, and white shrimp, Penaeus setiferus 

 (Linnaeus)," "Hydrological conditions in Clear 

 Lake, Texas, 1958-66," and "Channelization 

 and spoiling in Gulf coast and South Atlantic 

 estuaries ." 



Program personnel gave considerable atten- 

 tion during the year to assessment of the 

 probable effects of water-development activi- 

 ties. This responsibility was fulfilled by com- 

 pleting short-term investigations in connection 

 with the Federally planned as well as private 

 water-development projects. We worked in 



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